Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 221735
AFDRAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RALEIGH NC
1235 PM EST MON DEC 22 2014

.SYNOPSIS...A COLD AIR DAMMING RIDGE WILL REMAIN LOCKED IN PLACE
EAST OF THE APPALACHIANS THROUGH TUESDAY. A WARM FRONT WILL LIFT
NORTHWARD THROUGH THE REGION LATE TUESDAY NIGHT AND WEDNESDAY AS A
DEVELOPING LOW PRESSURE SYSTEM STRENGTHENS WEST OF THE MOUNTAINS.

&&

.NEAR TERM /TODAY THROUGH TUESDAY/...
AS OF 1055 AM MONDAY...

REST OF TODAY...LIFT ASSOCIATED WITH AN EXITING S/W WILL CONTINUE TO
LIFT INTO THE DELMARVA REGION THIS AFTERNOON...ESSENTIALLY ENDING
THE THREAT FOR WIDESPREAD LIGHT-MODERATE RAIN ACROSS THE NE PIEDMONT-
NORTHERN COASTAL PLAIN. IN THE WAKE OF THE S/W...A NEARLY SATURATED
LOW LEVEL AIR MASS WILL MAINTAIN EXTENSIVE LOW CLOUDS. WEAK
ISENTROPIC UPGLIDE 925-850MB WILL TEMPORARILY WANE THIS AFTERNOON.
THIS IS ALREADY EVIDENT IN THE LATEST ANALYSIS OF VAD WIND PROFILE
DATA AT 14Z-15Z. THUS...ASIDE FROM POCKETS OF DRIZZLE...EXPECT
MOSTLY DRY CONDITIONS THROUGH LATE AFTERNOON.

AFTERNOON TEMPERATURES STILL EXPECTED TO BE 12-16 DEGREES BELOW
NORMAL FOR THIS TIME OF YEAR DUE TO THE COLD DAMMING EVENT (HYBRID
OR CLASSICAL IN CLASSIFICATION) AS PARENT HIGH (1030-1033MB) IN
VICINITY OF THE NEW ENGLAND COAST/NOVA SCOTIA WILL PROVIDE A LOW
LEVEL SUPPLY OF COOL AIR INTO CENTRAL NC. AFTERNOON TEMPS MID-UPPER
30S IN THE PIEDMONT-LOWER 40S FAR SE. -WSS

TONIGHT/TUESDAY: ADDITIONAL SHORTWAVE ENERGY IN SW FLOW ALOFT IS
PROGGED TO TRACK NORTHEAST ACROSS WESTERN PORTIONS OF THE STATE
OVERNIGHT...AND THIS IS THE BASIS FOR AN INCREASED CHANCE FOR RAIN
AFTER MIDNIGHT... PRIMARILY WEST OF HWY 1. PRECIP ON TUESDAY WILL
DEPEND UPON THE TIMING/TRACK OF SHORTWAVE ENERGY IN SW FLOW
ALOFT...AND THE SUBTLE INFLUENCE THESE FEATURES WILL IMPART UPON LOW
LEVEL HEIGHT/WIND FIELDS. AS A RESULT...CONFIDENCE IS LOWER THAN
NORMAL WITH REGARD TO THE TIMING/AREAL EXTENT OF PRECIPITATION ON
TUE...LET ALONE PRECIP AMOUNTS. AT THIS TIME WILL INDICATE A 40-60%
CHANCE OF RAIN THROUGHOUT THE DAY...HIGHEST IN THE WESTERN PIEDMONT.
EXPECT TEMPERATURES TO LARGELY REMAIN STEADY DURING THE DAY
TUE...THOUGH PERHAPS BEGINNING TO RISE IN THE FAR SE COASTAL PLAIN
(I.E. SAMPSON COUNTY) BY SUNSET. -VINCENT

&&

.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
AS OF 235 AM MONDAY...

...WARM... WET... AND RATHER WINDY SYSTEM TO AFFECT OUR REGION
TUESDAY NIGHT THROUGH CHRISTMAS EVE... THEN WINDY AND COOLER
CHRISTMAS DAY...

MODELS AND ENSEMBLES DEPICT WITH HIGH CONFIDENCE THAT A WARM... WET
AND WINDY SYSTEM WILL AFFECT OUR REGION MID WEEK. THE MAIN SURFACE
STORM TRACK WILL BE FROM THE GULF OF MEXICO NORTHWARD THROUGH THE
TENNESSEE AND OHIO VALLEY REGIONS TUESDAY NIGHT INTO WEDNESDAY.
SINCE THE STORM WILL BE HEADING UP TO THE WEST OF THE APPALACHIANS
OUR REGION WILL HAVE TO DEAL WITH RESIDUAL COLD AIR DAMMING WHICH
APPEARS TO BE EVEN MORE LOCKED IN IN THE LATEST MODEL RUNS INTO
TUESDAY NIGHT (AND EVEN WEDNESDAY MORNING IN THE NW PIEDMONT). THE
MAIN COLD FRONT IS SLATED TO FOLLOW THE WARM FRONTAL PASSAGE
WEDNESDAY AFTERNOON AND NIGHT WITH SOME LINGERING TIMING DIFFERENCES
IN THE OPERATIONAL MODELS.

TIMING OF THESE WILL BE CRITICAL TO THE SENSIBLE WEATHER FORECASTS.
WE WILL MAINTAIN CONTINUITY FROM OUR PREVIOUS FORECASTS AND BLEND
WITH THE LATEST ENSEMBLE MEANS FROM THE GFS/EC TO GIVE IT OUR BEST
SHOT AT THE TIMING/STRENGTH OF THESE FEATURES.

TUESDAY NIGHT... RAIN EXPECTED TO BECOME WIDESPREAD FROM THE SOUTH
AND WEST AS THE WARM/WEDGE FRONT GRADUALLY LIFTS NORTH INTO THE
REGION. LINGERING COLD AIR DAMMING IS EXPECTED TO BE IN PLACE OVER A
GOOD PORTION OF THE PIEDMONT DAMMING REGION THROUGH 06Z/WEDNESDAY...
THEN GRADUALLY GIVE WAY TO THE WARM FRONT BETWEEN 06Z-12Z WEDNESDAY
AS THE MAIN STORM LIFTS UP THROUGH THE TENNESSEE VALLEY. RAINFALL
MAY BECOME HEAVY AIDED BY STRONG WAA LIFT UP AND OVER THE WARM
FRONT. LOWS WILL LIKELY BE EARLY IN THE NIGHT WITH RISING
TEMPERATURES IN ALL BUT THE FAR NW CORNER OVERNIGHT. TEMPS SHOULD
BEGIN THE EVENING IN THE LOWER 40S NW TO 50S SE... THEN RISE INTO
THE 60S SOUTH AND EAST BY 12Z/WED.

WEDNESDAY... THE WARM FRONT SHOULD LIFT INTO VIRGINIA. THIS WILL
LIKELY LEAD TO A LULL IN THE WARM FRONTAL RAINS AS THEY LIFT INTO
VIRGINIA WEDNESDAY AFTERNOON. HIGHS SHOULD RISE INTO THE 60S WEST
AND LOWER 70S EAST.

WEDNESDAY PM... THE MAIN COLD FRONT SHOULD ARRIVE BETWEEN 00Z/06Z
THURSDAY (WEDNESDAY NIGHT)... ACCOMPANIED BY ADDITIONAL SHOWERS AND
POSSIBLY A FEW THUNDERSTORMS (IF THE LOW LEVELS CAN DESTABILIZE
ENOUGH... WHICH IS IN DOUBT - GIVEN THE TIME OF YEAR. HOWEVER...
SURFACE DEW POINTS WEDNESDAY AFTERNOON IN THE WARM SECTOR SHOULD
REACH 60 OR EVEN 65 SE. BREEZY TO WINDY SW FLOW AT 10-25 MPH CAN BE
EXPECTED WITH TEMPS INTO THE 65-72 RANGE. THIS WOULD STILL ONLY
YIELD MUCAPES OF 100 TO 200 J/KG. IN ADDITION... THE STRONGEST LOW
LEVEL JET IS EXPECTED TO PUSH NORTHWARD INTO VA/MD BY EARLY
WEDNESDAY AFTERNOON ALONG THE RETREATING WARM FRONT. WITH THE MAIN
DYNAMICS PASSING OVER THE GREAT LAKES... THESE FACTORS WILL GREATLY
LIMIT ANY SEVERE POTENTIAL WITH THIS STORM FOR CENTRAL NC.

STORM TOTAL QPF OF 1 TO 1.5 INCHES IS EXPECTED WITH THIS EVENT
ENDING WEDNESDAY EVENING/NIGHT AS THE COLD FRONT PUSHES EAST OF THE
REGION. THIS WILL INTRODUCE A MUCH DRIER... COOLER AND WINDY
CHRISTMAS DAY.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
AS OF 225 AM MONDAY...

THE MAIN STORM AND COLD FRONT WILL SWEEP WELL OFFSHORE EARLY
THURSDAY. BREEZY TO WINDY CONDITIONS ON CHRISTMAS DAY WILL GRADUALLY
SUBSIDE AS A MILD PACIFIC ORIGIN HIGH WILL BUILD IN LATE IN THE DAY.
DRY AND SEASONABLY MILD CONDITIONS ARE EXPECTED AFTER THE WESTERLY
WINDS AT 15-25 MPH DIMINISH LATER THURSDAY AND FRIDAY. LOWS IN THE
30S AND HIGHS IN THE 50S ARE EXPECTED.

MODEL SPREAD REMAINS LARGE LATE FRIDAY THROUGH THE WEEKEND. THE
GFS/EC ENSEMBLE MEANS WERE BLENDED TO TRY TO CAPTURE A GENERAL
FORECAST GIVEN THE SPREAD IN THE MODELS. THIS YIELDS A COLD FRONTAL
PASSAGE SATURDAY WITH A WEAK WAVE POTENTIAL TO FOLLOW. THIS WOULD
GIVE AN INCREASE IN A CHANCE OF RAIN SUNDAY. P-TYPE IS NOT EXPECTED
TO BE A CONCERN AT THIS POINT... BUT AN EVEN COLDER AIR MASS IS
EXPECTED TO BE DRIVEN SE INTO OUR LATITUDE EARLY TO MID NEXT WEEK
(LIKELY AFTER THE SAID WAVE OF LOW PRESSURE SLIDES WELL OFFSHORE).
LOWS IN THE 30S AND HIGHS IN THE 40S SUNDAY WILL BE REPLACED BY LOWS
THE 20S AND HIGHS IN THE 40S MONDAY WITH DRIER CONDITIONS.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
AS OF 1235 PM MONDAY...

HIGH CONFIDENCE THAT IFR/LIFR CEILINGS AND VISIBILITIES WILL PERSIST
ACROSS CENTRAL NC THROUGH TUESDAY MORNING. A NEARLY SATURATED LOW
LEVEL AIR MASS ALONG WITH WEAK PERTURBATIONS ALOFT WILL MAINTAIN
EXTENSIVE LOW CLOUDS AND FOG ALONG WITH POCKETS OF LIGHT RAIN OR
DRIZZLE.

HIGH CONFIDENCE THAT ADVERSE AVIATION WEATHER CONDITIONS WILL
PERSIST TUESDAY MORNING THROUGH CHRISTMAS EVE. A SATURATED LOW LEVEL
AIR MASS WILL MAINTAIN THE EXTENSIVE LOW CLOUDS THROUGH TUESDAY
NIGHT. A STRONG LOW PRESSURE SYSTEM AND ATTENDANT SFC COLD FRONT
WILL INCREASE THE PROBABILITY OF SHOWERS LATE TUESDAY...CONTINUING
INTO WEDNESDAY...WITH PERIODS OF MODERATE-HEAVY RAIN POSSIBLE
TUESDAY NIGHT INTO EARLY WEDNESDAY.

THE COLD FRONT WILL CROSS CENTRAL NC CHRISTMAS EVE WITH NUMEROUS
SHOWERS AND A THUNDERSTORM OR TWO OCCURRING AHEAD OF IT. BEHIND THE
FRONT...BLUSTERY WESTERLY WINDS WILL OCCUR CHRISTMAS DAY WITH GUSTS
30-35KTS POSSIBLE. OTHERWISE VFR CONDITIONS EXPECTED TO RETURN
CHRISTMAS DAY AND PERSIST THROUGH SATURDAY.

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

SYNOPSIS...VINCENT
NEAR TERM...WSS/VINCENT
SHORT TERM...BADGETT
LONG TERM...BADGETT
AVIATION...WSS


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